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Anand Yethiraj

Bio: Anand Yethiraj is an academic researcher from St. John's University. The author has contributed to research in topics: Phase transition & Liquid crystal. The author has an hindex of 22, co-authored 72 publications receiving 2381 citations. Previous affiliations of Anand Yethiraj include University of British Columbia & Fundamental Research on Matter Institute for Atomic and Molecular Physics.


Papers
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Journal ArticleDOI
20 Jul 2015-Langmuir
TL;DR: This analysis presents a unified strategy for comparing structural order among different colloidal crystals and establishes benchmarks for future studies, finding that translational measures are adequate for characterizing small deviations from perfect order, whereas orientation measures are more informative for polycrystalline and highly disordered crystals.
Abstract: Although there are numerous self-assembly techniques to prepare colloidal crystals, there is great variability in the methods used to characterize order and disorder in these materials. We assess different kinds of structural order from more than 70 two-dimensional microscopy images of colloidal crystals produced by many common methods, including spin-coating, dip-coating, convective assembly, electrophoretic assembly, and sedimentation. Our suite of analysis methods includes measures for both positional and orientational order. The benchmarks are two-dimensional lattices that we simulated with different degrees of controlled disorder. We find that translational measures are adequate for characterizing small deviations from perfect order, whereas orientational measures are more informative for polycrystalline and highly disordered crystals. Our analysis presents a unified strategy for comparing structural order among different colloidal crystals and establishes benchmarks for future studies.

11 citations

Journal ArticleDOI
TL;DR: In this article, the structure and dynamics in sedimentation equilibrium, in the presence of gravity, were examined via confocal microscopy, for a Brownian colloidal system with an external electric field.
Abstract: In this work, we use structure and dynamics in sedimentation equilibrium, in the presence of gravity, to examine, via confocal microscopy, a Brownian colloidal system in the presence of an external electric field. The zero field equation of state (EOS) is hard sphere without any re-scaling of particle size, and the hydrodynamic corrections to the long-time self-diffusion coefficient are quantitatively consistent with the expected value for hard spheres. Care is taken to ensure that both the dimensionless gravitational energy, which is equivalent to a Peclet number Peg, and dipolar strength Λ are of order unity. In the presence of an external electric field, anisotropic chain-chain clusters form; this cluster formation manifests itself with the appearance of a plateau in the diffusion coefficient when the dimensionless dipolar strength Λ ~ 1. The structure and dynamics of this chain-chain cluster state is examined for a monodisperse system for two particle sizes.

11 citations

Journal ArticleDOI
TL;DR: This work finds that the electric capillary number, CaE, at the threshold of drop breakup is of order unity for cell thicknesses of 100 μm or thicker, but much larger for thinner cells, and there is a clear transition to super-diffusive droplet motions above this threshold.
Abstract: A two-fluid emulsion (silicone oil drops in the “leaky dielectric”, castor oil) with electrohydrodynamically driven flows can serve as a model system for tunable studies of hydrodynamic interactions [Varshney et al., Sci. Rep., 2012, 2, 738]. Flows on multiple length- and time-scales have been observed but the underlying mechanism for these chaotic, multi-scale flows is not understood. In this work, we conducted experiments varying the thickness of the test cell to examine the role of substrate interactions on size distribution, mean square displacement and velocity of the drops as a function of the electric field strength. We find that the electric capillary number, CaE, at the threshold of drop breakup is of order unity for cell thicknesses of 100 μm or thicker, but much larger for thinner cells. Above this threshold, there is a clear transition to super-diffusive droplet motions. In addition, we observe that there is a convective instability prior to the onset of chaotic flows, with the lengthscale associated with the convection rolls increasing linearly with an increase in the cell thickness. The fact that the convective instability appears to occur in the leaky dielectric castor oil regardless of whether the second component is liquid drops, solid particles, or dissolved dye has implications on the underlying mechanism for the unsteady flows.

11 citations

Journal ArticleDOI
TL;DR: It is found, via different measures of macromolecular mobility, that the mobility of the flexible polymer in the crowding limit is 10-100 times larger than that of the compact, spherical crowder in spite of their similar size, implying that the flexiblepolymer chain is able to squeeze through crowder interstices.
Abstract: We have examined the effect of crowder particle charge on macromolecular structure, studied via small-angle neutron scattering, and translational dynamics, studied via pulsed-field gradient NMR, in...

11 citations

Book ChapterDOI
01 Jan 2001
TL;DR: In this paper, it was shown that metallo-dielectric structures should also have very interesting photonic properties in the visible, including, if one neglects absorption, a complete band gap.
Abstract: Photonic crystals are regular three-dimensional (3D) structures with which the propagation and spontaneous emission of photons can be manipulated in new ways if the feature sizes are roughly half the wavelength and the coupling with the electromagnetic radiation is sufficiently strong. ‘Early’ speculation on these new possibilities can be found in the Refs.1–4 A more recent overview can be found in Ref.5 and, of course, the other chapters in this book. A useful analogy to guide thinking about the properties and the applications of photonic crystals is the propagation of electrons in a semiconductor in comparison to the propagation of photons scattered by a regular 3D dielectric material. An example is the possibility of opening up a region of energy, a photonic band gap, for which the propagation of photons is forbidden, in analogy to the electronic band gap present in semiconductors. However, there are also important differences; for instance, the scattering of photons cannot be described well by scalar wave equations because the polarization of light cannot be neglected. Most theoretical and experimental work for visible light applications have until now focused on pure dielectric structures, interestingly, recent calculations have shown that metallo-dielectric structures should also be considered as having very interesting photonic properties in the visible, including, if one neglects absorption, a complete band gap.6–8 And even with absorption taken into account, it seems that for relatively thin photonic crystals most of the interesting optical properties remain.8

10 citations


Cited by
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28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1(PfPMP1)与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员,通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

18,940 citations

Journal ArticleDOI
TL;DR: This work argues for a conceptual framework for these new building blocks based on anisotropy attributes and discusses the prognosis for future progress in exploiting an isotropy for materials design and assembly.
Abstract: A revolution in novel nanoparticles and colloidal building blocks has been enabled by recent breakthroughs in particle synthesis These new particles are poised to become the ‘atoms’ and ‘molecules’ of tomorrow’s materials if they can be successfully assembled into useful structures Here, we discuss the recent progress made in the synthesis of nanocrystals and colloidal particles and draw analogies between these new particulate building blocks and better-studied molecules and supramolecular objects We argue for a conceptual framework for these new building blocks based on anisotropy attributes and discuss the prognosis for future progress in exploiting anisotropy for materials design and assembly

2,558 citations

Journal ArticleDOI
20 Jan 2011-Nature
TL;DR: This paper shows how colloidal spheres can be induced to self-assemble into a complex predetermined colloidal crystal—in this case a colloidal kagome lattice—through decoration of their surfaces with a simple pattern of hydrophobic domains, and encodes the target supracolloidal architecture.
Abstract: A challenging goal in materials chemistry and physics is spontaneously to form intended superstructures from designed building blocks. In fields such as crystal engineering and the design of porous materials, this typically involves building blocks of organic molecules, sometimes operating together with metallic ions or clusters. The translation of such ideas to nanoparticles and colloidal-sized building blocks would potentially open doors to new materials and new properties, but the pathways to achieve this goal are still undetermined. Here we show how colloidal spheres can be induced to self-assemble into a complex predetermined colloidal crystal-in this case a colloidal kagome lattice-through decoration of their surfaces with a simple pattern of hydrophobic domains. The building blocks are simple micrometre-sized spheres with interactions (electrostatic repulsion in the middle, hydrophobic attraction at the poles, which we call 'triblock Janus') that are also simple, but the self-assembly of the spheres into an open kagome structure contrasts with previously known close-packed periodic arrangements of spheres. This open network is of interest for several theoretical reasons. With a view to possible enhanced functionality, the resulting lattice structure possesses two families of pores, one that is hydrophobic on the rims of the pores and another that is hydrophilic. This strategy of 'convergent' self-assembly from easily fabricated colloidal building blocks encodes the target supracolloidal architecture, not in localized attractive spots but instead in large redundantly attractive regions, and can be extended to form other supracolloidal networks.

1,125 citations

Journal ArticleDOI
25 Nov 2004-Nature
TL;DR: It is demonstrated that in both model systems, a combination of short-range attraction and long-range repulsion results in the formation of small equilibrium clusters, which is relevant for nucleation processes during protein crystallization, protein or DNA self-assembly.
Abstract: Controlling interparticle interactions, aggregation and cluster formation is of central importance in a number of areas, ranging from cluster formation in various disease processes to protein crystallography and the production of photonic crystals. Recent developments in the description of the interaction of colloidal particles with short-range attractive potentials have led to interesting findings including metastable liquid-liquid phase separation and the formation of dynamically arrested states (such as the existence of attractive and repulsive glasses, and transient gels). The emerging glass paradigm has been successfully applied to complex soft-matter systems, such as colloid-polymer systems and concentrated protein solutions. However, intriguing problems like the frequent occurrence of cluster phases remain. Here we report small-angle scattering and confocal microscopy investigations of two model systems: protein solutions and colloid-polymer mixtures. We demonstrate that in both systems, a combination of short-range attraction and long-range repulsion results in the formation of small equilibrium clusters. We discuss the relevance of this finding for nucleation processes during protein crystallization, protein or DNA self-assembly and the previously observed formation of cluster and gel phases in colloidal suspensions.

967 citations